Python实现简单状态框架的方法
本文实例讲述了Python实现简单状态框架的方法。分享给大家供大家参考。具体分析如下：
这里使用Python实现一个简单的状态框架，代码需要在python3.2环境下运行
fromtimeimportsleep
fromrandomimportrandint,shuffle
classStateMachine(object):
'''Usage: CreateaninstanceofStateMachine,useset_starting_state(state)togiveitan
initialstatetoworkwith,thencalltick()oneachsecond(orwhateveryourdesired
timeintervalmightbe.'''
defset_starting_state(self,state):
'''Theentrystateforthestatemachine.'''
state.enter()
self.state=state
deftick(self):
'''Callsthecurrentstate'sdo_work()andchecksforatransition'''
next_state=self.state.check_transitions()
ifnext_stateisNone:
#Stickwiththisstate
self.state.do_work()
else:
#Nextstatefound,transitiontoit
self.state.exit()
next_state.enter()
self.state=next_state
classBaseState(object):
'''Usage:SubclassBaseStateandoverridetheenter(),do_work(),andexit()methods.
enter() --Setupforyourstateshouldoccurhere. Thislikelyincludesadding
transitionsorinitializingmembervariables.
do_work() --Meatandpotatoesofyourstate. Theremaybesomelogicherethatwill
causeatransitiontotrigger.
exit() --Anycleanuporfinalactionsshouldoccurhere. Thisiscalledjust
beforetransitiontothenextstate.
'''
defadd_transition(self,condition,next_state):
'''Addsanewtransitiontothestate. The"condition"parammustcontainacallable
object. Whenthe"condition"evaluatestoTrue,the"next_state"paramissetas
theactivestate.'''
#Enforcetransitionvalidity
assert(callable(condition))
assert(hasattr(next_state,"enter"))
assert(callable(next_state.enter))
assert(hasattr(next_state,"do_work"))
assert(callable(next_state.do_work))
assert(hasattr(next_state,"exit"))
assert(callable(next_state.exit))
#Addtransition
ifnothasattr(self,"transitions"):
self.transitions=[]
self.transitions.append((condition,next_state))
defcheck_transitions(self):
'''ReturnsthefirstStatethatsconditionevaluatestrue(conditionorderisrandomized)'''
ifhasattr(self,"transitions"):
shuffle(self.transitions)
fortransitioninself.transitions:
condition,state=transition
ifcondition():
returnstate
defenter(self):
pass
defdo_work(self):
pass
defexit(self):
pass
##################################################################################################
###############################EXAMPLEUSAGEOFSTATEMACHINE###################################
##################################################################################################
classWalkingState(BaseState):
defenter(self):
print("WalkingState:enter()")
defcondition():returnrandint(1,5)==5
self.add_transition(condition,JoggingState())
self.add_transition(condition,RunningState())
defdo_work(self):
print("Walking...")
defexit(self):
print("WalkingState:exit()")
classJoggingState(BaseState):
defenter(self):
print("JoggingState:enter()")
self.stamina=randint(5,15)
defcondition():returnself.stamina<=0
self.add_transition(condition,WalkingState())
defdo_work(self):
self.stamina-=1
print("Jogging({0})...".format(self.stamina))
defexit(self):
print("JoggingState:exit()")
classRunningState(BaseState):
defenter(self):
print("RunningState:enter()")
self.stamina=randint(5,15)
defwalk_condition():returnself.stamina<=0
self.add_transition(walk_condition,WalkingState())
deftrip_condition():returnrandint(1,10)==10
self.add_transition(trip_condition,TrippingState())
defdo_work(self):
self.stamina-=2
print("Running({0})...".format(self.stamina))
defexit(self):
print("RunningState:exit()")
classTrippingState(BaseState):
defenter(self):
print("TrippingState:enter()")
self.tripped=False
defcondition():returnself.tripped
self.add_transition(condition,WalkingState())
defdo_work(self):
print("Tripped!")
self.tripped=True
defexit(self):
print("TrippingState:exit()")
if__name__=="__main__":
state=WalkingState()
state_machine=StateMachine()
state_machine.set_starting_state(state)
whileTrue:
state_machine.tick()
sleep(1)
希望本文所述对大家的Python程序设计有所帮助。